Color variation has not been the first thing you think of when you look at US bank notes. A wan touch of green, sure. But nothing remotely Fauvist—and certainly, please, no Day-Glo psychedelic swirls.

The new bill, which will be introduced in October, is the latest in a series of subtle redesigns of other US bank notes, some of which have cautiously allowed tiny amounts of color. This one, by contrast, has a big fat stripe of blue, and a bright gold inkpot.

If it’s the beginning of a revolution, it’s a revolution that has swept through many other countries already. Elsewhere, colored currency is commonplace. But here in the United States people seem to regard color as fundamentally unserious. Tell them to show you the color of their money, and they’ll present their pale, color-drained cash with a flinty look that says: This is the real stuff.

Negative feelings about color have a long history of their own, one that stretches well beyond currency. Over the centuries, artists associated with adamantine line (Michelangelo, Poussin, Ingres) have always epitomized masculine sobriety, whereas their rivals who relished the flux of color (Titian, Rubens, Delacroix) courted accusations of frivolity and femininity.

Even after the modernist revolution, the most momentous feature of which was the liberation of color, staunchly linear artists continued to lord it over great colorists. Picasso—a klutz with color—was easier for critics to take seriously than Matisse. “Guernica,” Picasso’s famous response to a Spanish Civil War atrocity, was painted in black and white for a reason.

The US dollar can afford most things—including endless self-replication—but it cannot afford to appear unserious. And so, even as other currencies have embraced the delights (and obstacles to counterfeiting) afforded by vivid color, the US dollar has remained obstinately nondescript.

“It looks like Monopoly money!”

That’s the refrain most commonly heard by traveling Australians who dare to display the unexchanged contents of their wallets. Australia, where I’m from, was the first country to invent and introduce, in 1988, the polymer bank note, the virtues of which are legion: It’s hard to forge, it incorporates more security features, it lasts much longer than a paper note, and you can take it surfing (you never know when you might need a buck).

But Australia’s polymer bank notes are also ridiculously colorful. Even though, according to current exchange rates, they are worth almost exactly the same as US dollars, their colors make them an international joke. Informed of their virtues, people just don’t seem impressed. They giggle, and seem to think they’re in a movie—“Crocodile Dundee Rides Again.”

But all this may be changing. Bermuda, Brunei, Papua New Guinea, Romania—oh, and Canada—have all seen the writing on the wall and introduced colorful polymer bank notes.

And now here we have one of the world’s most famous design icons, the US bank note—incarnation of the most closely watched and consequential of currencies—loosening up, getting frisky, turning blue.

What does it signify? Could it be that the whole world is beginning to take color more seriously? Will we soon see the business districts of the great financial centers overrun with sober-faced bankers dressed in Day-Glo colors with zinging Benday dots?

Not likely. Rather, it’s simply a subtle sign that the venerable Federal Reserve is starting to get real. No longer does it feel obliged to keep up this fake front of monochrome sobriety and steadfast reliability. Credit default swaps and crashing banks put an end to all that.

Quietly, with the teeniest blush of pink beguiling its cheeks, the Federal Reserve is ready to admit: This stuff is Monopoly money.